The Education of Uncle Paul

As described in Clute & Grant's An Encyclopedia of Fantasy, this "is a novel for adults about children; it explores the land of lost childhood on the threshold between today and tomorrow. This novel was later adapted for the stage by Violet Pearn as "Through the Crack" (produced 1920; 1925), and the theme was reworked by Blackwood himself in The Extra Day (1915) and The Fruit Stoners (1934).